Cooling system,radiator fan

Check for leaks,possibly pressure test on system,to see why it,s lost coolant,block test for cylinder head issue,s.

Could test thermostat , check rad not partially blocked .A pressure test should show any external leaks causing drop in header tank level. A block test will check head /gasket .

if coolant level is low or has been low system will have an air lock so fan will run as above check for leaks problem areas are water pump leak /inlet manifold gasket leak rectify and blead out cooling system make sure heater in car is nice and hot problem is if these engines are overheated it damages the special rubber bead on the head gasket this in turn will eventually cause mixing of coolant and oil into the engine or into the cooling system depending on where the sealing bead has failed so never let coolant level drop on these engines check level on a regular basis